In the past, glass antennas for vehicles in which a VHF band antenna is formed on the window glass of the vehicle have been known, as disclosed for example in Japanese Patent Application Laid-Open Publication No. 2001-136013 (JP 2001-136013 A).
The glass antenna disclosed in JP 2001-136013 A is shown in FIG. 1 hereof. In this glass antenna, the VHF antenna (FM antenna) 2 has an antenna element 4 comprising a conductor element that is bent in a U shape in order to ensure the antenna length (λ/4=approximately 830 mm) that is required for reception in the VHF band. One end of the U-shaped antenna element 4 is connected to a rectangular feeder terminal 6. The other end of the antenna element 4 is grounded to a rectangular ground terminal 8. The reference symbol 10 indicates a side window glass of the vehicle.
The feeder terminal 6 is connected to a feeder line (coaxial cable) 14. The ground terminal 8 is connected to a conductor (vehicle body) 12 that forms the opening used for the window glass 10 via a feeder line (wire) 15.
The glass antenna disclosed in JP 2001-136013 A has a ground terminal 8 in order to match the impedance of the glass antenna with the impedance of the feeder line 14. In this glass antenna, since a ground terminal 8 connected to the vehicle body 12 is provided on the window glass 10, the glass antenna has an antenna impedance suitable for antenna reception even if the area of the vehicle window glass is small, and use in the side window glass of an automobile is possible.
However, in the case of vehicles in which the area of the window glass is even smaller, e.g., 0.10 to 0.15 m2 (narrow area) matching with the impedance of the feeder line cannot be achieved, and an effective reception performance cannot be obtained.